U.S. Pat. No. 4,400,293 (Romer et al) discloses cyclohexylphenyl "derivatives" with a sulfur moiety and halogen-substituted ring. The general formula is: ##STR5## X can be S--CH.sub.2 ; R.sub.2, R.sub.3, R.sub.4 can be chlorine. The compounds are used as electro-optical indicators based on the changes in their optical properties under the influence of electric fields.
U.S. Pat. No. 3,650,760 (Gates, Jr., et al) discloses alkoxy mercaptophenols used in photographic silver halide emulsions in order to stabilize the emulsions.
U.S. Pat. No. 4,136,102 (Crivello) disclosed halogen onium salts which exhibit unusual activity under UV light and can be employed as cationic photoinitiators.
U.S. Pat. No. 3,932,527 (Metcalf et al) which discloses the preparation of p-p' Disubstituted diaryl trichloroethanes for insectidal purposes.
U.S. Pat. No. 3,114,777 (Reifschneider) discloses Tolylbisthioethers of general formula: ##STR6## wherein R, R' and R" are alkyl groups.
U.S. Pat. No. 3,879,472 (Martin) discloses alkyl sulfides, sulfoxides and sulfones of general formula: ##STR7## where: X can be Cl, and
R.sub.1, R.sub.2 and R.sub.3 are alkyl groups.
U.S. Pat. No. 3,686,331 (O'Brien et al) discloses phenyl 3-halopropargyl ethers useful as anti-bacterial and antifungicidal agents.
U.S. Pat. No. 4,108,906 (Anderson) discloses a halogenated aryl compound of general formula: ##STR8## where R can be ##STR9## and M and M' can be sulfur (Z.sub.m can be ClBr), thus making a possible compound of: ##STR10## where the A group is --OCH.sub.3
The present invention in its most important aspect relates to novel compositions which are reversible photochromic solids.
The most important practical application of reversible photochromism is information storage by use of lasers.
The state of the art in photo-information storage is the use of tellurium suboxide. Irradiation of this material converts it reversibly to tellurium. The difference between tellurium and its suboxide can then be discerned and thus information can be stored and read (as tellurium). Another state of the art photo storage involves organic photochromics (spirobenzopyrans). These systems have certain drawbacks. Tellurium is highly toxic and the spiropyrans "fatigue" after a few cycles.
We have discovered that molecules having the formula: ##STR11## wherein: X=Cl, Y= ##STR12## X=Y= ##STR13## X=Y= ##STR14## R=hydrogen, halogen such as chlorine, lower alkoxy such as methoxy, or lower alkyl such as methyl,
undergo a color change upon irradiation (photochromism). This discovery was applied to the invention of reversible (thermal bleaching) photochromism by a conformational change.
The particular advantage of our system over the state of the art Brown, G. H., Ed. "Photochromism", Wiley Interscience, 1971; Vol. 3 is that no photochemistry occurs during photochromism. Photochemistry requires making and breaking of covalent chemical bonds. This is a relatively high energy process which ultimately becomes irreversible. Our discovery involves simple movement of parts of a molecule; energetically much less demanding and consequently of greater and longer lasting reversibility. It is to be expected that the present invention will be widely adapted by those skilled in the art.